package org.springframework.jdbc.datasource;

import lombok.extern.slf4j.Slf4j;
import org.springframework.lang.Nullable;
import org.springframework.transaction.CannotCreateTransactionException;
import org.springframework.transaction.NestedTransactionNotSupportedException;
import org.springframework.transaction.SavepointManager;
import org.springframework.transaction.TransactionException;
import org.springframework.transaction.TransactionSystemException;
import org.springframework.transaction.TransactionUsageException;
import org.springframework.transaction.support.SmartTransactionObject;
import org.springframework.util.Assert;

import java.sql.SQLException;
import java.sql.Savepoint;

/**
 * Convenient base class for JDBC-aware transaction objects. Can contain a
 * {@link ConnectionHolder} with a JDBC {@code Connection}, and implements the
 * {@link SavepointManager} interface based on that {@code ConnectionHolder}.
 *
 * <p>Allows for programmatic management of JDBC {@link java.sql.Savepoint Savepoints}.
 * Spring's {@link org.springframework.transaction.support.DefaultTransactionStatus}
 * automatically delegates to this, as it autodetects transaction objects which
 * implement the {@link SavepointManager} interface.
 *
 * @author Juergen Hoeller
 * @since 1.1
 * @see DataSourceTransactionManager
 */
@Slf4j
public abstract class JdbcTransactionObjectSupport implements SavepointManager, SmartTransactionObject {
    private ConnectionHolder connectionHolder;

    private Integer previousIsolationLevel;

    private boolean readOnly = false;

    private boolean savepointAllowed = false;

    /**
     * Set the ConnectionHolder for this transaction object.
     */
    public void setConnectionHolder(@Nullable ConnectionHolder connectionHolder) {
        this.connectionHolder = connectionHolder;
    }

    /**
     * Return the ConnectionHolder for this transaction object.
     */
    public ConnectionHolder getConnectionHolder() {
        Assert.state(this.connectionHolder != null, "No ConnectionHolder available");
        return this.connectionHolder;
    }

    /**
     * Check whether this transaction object has a ConnectionHolder.
     */
    public boolean hasConnectionHolder() {
        return (this.connectionHolder != null);
    }

    /**
     * Set the previous isolation level to retain, if any.
     */
    public void setPreviousIsolationLevel(@Nullable Integer previousIsolationLevel) {
        this.previousIsolationLevel = previousIsolationLevel;
    }

    /**
     * Return the retained previous isolation level, if any.
     */
    @Nullable
    public Integer getPreviousIsolationLevel() {
        return this.previousIsolationLevel;
    }

    /**
     * Set the read-only status of this transaction.
     * The default is {@code false}.
     * @since 5.2.1
     */
    public void setReadOnly(boolean readOnly) {
        this.readOnly = readOnly;
    }

    /**
     * Return the read-only status of this transaction.
     * @since 5.2.1
     */
    public boolean isReadOnly() {
        return this.readOnly;
    }

    /**
     * Set whether savepoints are allowed within this transaction.
     * The default is {@code false}.
     */
    public void setSavepointAllowed(boolean savepointAllowed) {
        this.savepointAllowed = savepointAllowed;
    }

    /**
     * Return whether savepoints are allowed within this transaction.
     */
    public boolean isSavepointAllowed() {
        return this.savepointAllowed;
    }

    @Override
    public void flush() {
        // no-op
    }


    //---------------------------------------------------------------------
    // Implementation of SavepointManager
    //---------------------------------------------------------------------

    /**
     * This implementation creates a JDBC 3.0 Savepoint and returns it.
     * @see java.sql.Connection#setSavepoint
     */
    @Override
    public Object createSavepoint() throws TransactionException {
        ConnectionHolder conHolder = getConnectionHolderForSavepoint();
        try {
            if (!conHolder.supportsSavepoints()) {
                throw new NestedTransactionNotSupportedException(
                        "Cannot create a nested transaction because savepoints are not supported by your JDBC driver");
            }
            if (conHolder.isRollbackOnly()) {
                throw new CannotCreateTransactionException(
                        "Cannot create savepoint for transaction which is already marked as rollback-only");
            }
            return conHolder.createSavepoint();
        }
        catch (SQLException ex) {
            throw new CannotCreateTransactionException("Could not create JDBC savepoint", ex);
        }
    }

    /**
     * This implementation rolls back to the given JDBC 3.0 Savepoint.
     * @see java.sql.Connection#rollback(java.sql.Savepoint)
     */
    @Override
    public void rollbackToSavepoint(Object savepoint) throws TransactionException {
        ConnectionHolder conHolder = getConnectionHolderForSavepoint();
        try {
            conHolder.getConnection().rollback((Savepoint) savepoint);
            conHolder.resetRollbackOnly();
        }
        catch (Throwable ex) {
            throw new TransactionSystemException("Could not roll back to JDBC savepoint", ex);
        }
    }

    /**
     * This implementation releases the given JDBC 3.0 Savepoint.
     * @see java.sql.Connection#releaseSavepoint
     */
    @Override
    public void releaseSavepoint(Object savepoint) throws TransactionException {
        ConnectionHolder conHolder = getConnectionHolderForSavepoint();
        try {
            conHolder.getConnection().releaseSavepoint((Savepoint) savepoint);
        }
        catch (Throwable ex) {
            log.debug("Could not explicitly release JDBC savepoint", ex);
        }
    }

    protected ConnectionHolder getConnectionHolderForSavepoint() throws TransactionException {
        if (!isSavepointAllowed()) {
            throw new NestedTransactionNotSupportedException(
                    "Transaction manager does not allow nested transactions");
        }
        if (!hasConnectionHolder()) {
            throw new TransactionUsageException(
                    "Cannot create nested transaction when not exposing a JDBC transaction");
        }
        return getConnectionHolder();
    }
}
